Hi Conch-L'ers,

Thanks to everyone for their comments regarding
the olives and Cone Wars.  Special thanks also
to our illustrious COA Bulletin editor (just joking)
who sent the following amazing and informative
e-mail.  It's too good to keep to myself, and gives
some great insight into what I saw involving the
Oliva miniacea and the Strombus gibberulus.

The only thing I can't resolve is the olive's reported
"blindness," or the olive's difficulty locating prey.
In the Cone Wars II episode, Lynn obviously knew
where the Strombus luhuanus was (she was prac-
tically swimming over the bottom toward it) and
she curled up her propodia, if that is what it was,
before she reached the Strombus gibberulus that
she engulfed.  By the way, when I got home from
work tonight, my wife told me that all the little
Strombus were jumping against the glass again,
and when she went to look that the Oliva miniacea
was out chasing them.  When I checked the tank,
I found only one Strombus gibberulus left...


Lynn Scheu wrote:

(regarding olives)...I had read that they would grab
small (that is small) molluscs and tuck them in
their pouch and go under the sand and eat them,
just as Bob Lipe says.

Here is what Kilburn and Rippey say in Seashells
of Southern Africa:

"Members of this family burrow in clean or muddy
sand, often in colonies, ...Their eyes are small or
even absent, the foot is very large and wide, and
in some species cannot be retracted into the shell.
When burrowing the sides of the foot (not the man-
tle as sometimes claimed) are partially folded over
the shell; the front of the foot is differentiated into a
highly dextrous propodium. By flapping this or the
side flaps up and down, members of several genera
are able to swim in a clumsy fashion, enabling them
to escape from predators. Some if not all Oliva can
secrete an evil smelling liquid, which turns purple
on exposure, as a defensive measure.

"Olividae will devour dead animal matter (they are
frequently collected with baited traps), but also prey
on living molluscs and small crustaceans. These
are seized with the front of the foot and enclosed in
a pocket formed by the posterior end of the sole, to
be dragged around for intermittent consumption.
Prey capture may involve the use of salivary toxins
as in the Volutidae."

Now to the Big Guns of The Southern Synthesis:
(by Brian Smith)

First indication that their doing this trick is known:
"The central nervous system in Olivella shows
distinct separation of the ganglia with fairly long
interganglionic connectives.  This makes it possible
for the oesophagus and nerve ring to be distended
when the animal swallows whole bivalves."

However that is Olivella. Get this:  "The ganglia of
Oliva are almost touching with very short connec-
tives forming a rigid nerve ring. This only permits
limited distension of the oesophagus, the animals
feeding on small fragments rasped from the prey,
or small animals or liquified food." !! That is old info
however.  (Marcus, Ev. and Marcus, Er. 1959b)

Zeigler and Porreca have a photo sequence of an
Oliva engulfing a shrimp (dead) in its pouch and
heading under the sand. A report by an aquarium
keeper of olives in Miami (Olsson and Crovo, 1968)
bears out the lack of visual acuity...says they will
pass and repass a morsel of food before they find
it, probably using their siphon, not their eyes. Ooh
hey, could this be what you saw:

"The moment the food morsel is discovered and
touched by the propodium, it is quickly seized in
the following manner. The forepart of the foot
curves over the foot and pushes it under and to
the rear, while the posterior portion of the foot is
brought forward, shaping into a pouch.  The fore-
foot pushes the food back to the rear of the pouch,
and often if the food portions are small, the olive
will pick up another piece and tuck it in with the
first. Olsson and Crovo described this procedure
as follows...'pushed back in its foot and enfolded
in its hinder section as if tucked away in a pocket,
which swells up into a rounded ball, the food item
hidden away so completely that no part of it is
visible externally.'  This same procedure is used
with live mollusks, the whole shell being scooped
back into the pouch. Mrs Crovo writes that, 'the
ability to stretch over the larger shell of the
Laevicardium is truly amazing as the pouch seems
to stretch to the thinness of a blown up balloon.'
Olives have been known to engulf egg cockles,
apparently one of their favorite foods, nearly as
large as themselves. The olive, after capturing its
prey or morsel, promptly retreats head first below
the sand to eat, Mrs.Crovo noted."

"I find them a fascinating study, wish more of the
human race had such good habits. They do not
kill each other under any circumstances, neither
do they eat a comrade if it dies, they only kill
other mollusks for food and they share whatever
they have for food with any and all who come to
eat." --Ellen Crovo

I also have Petuch's Atlas of the living Olividae,
in which he recaps Zeigler and Porreca, and three
other relevant works on Olividae:

Proc ANSP 108 1956 "Studies on the Genus
Olivella" in which he discusses General Ecol-
ogy and Habits,

Dietmar Greifeneder's "What Do We know About
Olividae" section of Contributions to the study of
OLIVIDAE by Greifeneder, Skinner, Widmer and
Hemmen in Acta Conchyliorum No. 1 1981,

and Tursch's April 1991 Studies on Olividae XIII
Behavior of Oliva vidua in aquarium: preliminary
observations in Apex (I have a lot of other Apex
Olividae articles but they are mostly taxonomic
or attempts to establish procedures for morpho-
metric analysis.  And one on color change in-
duced by substrate color change.)

The Tursch study is interesting anf to the point.
(O. vidua clocked at 25 cm/minute on a glass
substrate!!!)  One new piece of info I discovered
in Tursch was that they now think the critters
used their propodium as a sensory organ:

"The observation that food is not located by the
siphon but probably by the anterior edge of the
propodium deserves comment. Marcus and
Marcus have already observed that this part is
richly innervated (1959) and have concluded:
'...the much richer innervation of the propodial
border suggests that also in the Oliva this bor-
der is the most important sense organ...'.  This
would make sense as the siphon is generally
out of the sand where Oliva vidua must find its
prey."  Interpret that how you will. I presume it
means they find food under the sand, and the
siphon is used to detect predators? There are
drawings of the ventral view of the O vidua on
glass, showing pouch location, and O vidua
snacking from its pouch, while on glass. Can
scan. All sorts of stuff about preferences for
substrate, shade, water current, etc...

Also, the feeding behavior varies...in O.
sayana the prey is not eaten from the pouch
but released and fed upon (quoted from Z & P)

[and about Lynn Miniacea and the Strombus]:

All I read pretty much indicated that that nerve
ring in Oliva prevents swallowing the whole
prey critter. It was said many times in various
ways. If she started shoving him back within
a longitudinally in-curled foot (it would seem to
me to be tubelike in appearance if the olive did
that...get the picture?) the pouch is in the sole
of the foot, most of the way back, a longitudinal
slit.  I sort of understood that the pouch was
FORMED at will by curling up the foot from
earlier things I had read, but not so, it seems...
it would seem to be an anatomical feature.

Also about diving underground immediately
after, I would say the "immediately after"
referred to the time the conch was in the
pouch, not enveloped by the foot and being
transferred to the pouch. So she wasn't ready
to burrow under til she did that muscle trick
to shove the conch all the way in.

I also read that they slime the prey that goes
in the pouch. Sometimes they'll reject the
pouch contents (often in the case of live
olivellas) and other olives won't touch some-
thing that has been slimed. And one refer-
ence said that bivalves that had been slimed
were goners. There wasn't much on them
eating gastropods. So I would guess this
slime is a digestive enzyme or toxic sub-
stance that whaps the prey in the pouch.
There was some reference in something I
read to "meat juices" too, to the effect that
this was an important part of their diet...
maybe the slime dissolves portions of the
prey in the pouch and the olive slurps it
from the pouch...

Lynn